HR: 14:00h
AN: NB43A-03    [Abstracts]
TI: Scaling by Reference Conditions for Ecological Assessment
AU: Prins, S
EM: sprins@vt.edu
AF: Department of Statistics, Virginia TEch, Blacksburg, VA 24061 United States
AU: * Smith, E
EM: epsmith@vt.edu
AF: Department of Statistics, Virginia TEch, Blacksburg, VA 24061 United States
AB: Reference sites provide important information about the range of biological, physical and chemical measurements. Using reference information to scale data from other sites is useful for evaluating the status of sites and establishing impairment. A common approach is to use all the data on the reference conditions to standardize measurements for a new site. Rather than using all available reference sites to scale the observed value of a particular metric at a non-reference site, we present an alternative approach uses only the k closest (in terms of selected predictors) reference sites. These selected predictors may include only natural variables (for instance latitude and longitude), only potential stressors, or a combination of both and these variables may be continuous or categorical. We believe this nearest neighbors based distribution of the metric at a non-reference site is closer to the proper reference distribution for that site. Using benthic data from the Mid-Atlantic Highlands, we show that the nearest neighbor method improved on the ability of the existing approach to classify non-reference sites correctly and performed comparably on reference sites. We discuss issues related to the choice of k and present results suggesting an optimal k in this application.
DE: 0840 Evaluation and assessment
DE: 0910 Data processing
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly